A lot of progress.

src/fitter.rs

@@ -1,11 +1,21 @@
-mod batch;
 mod recursive;
 
-pub use batch::BatchFitter;
 pub use recursive::RecursiveFitter;
 
 pub trait Fitter {
     fn add_sample(&mut self, t: f64) -> usize;
     fn allocate(&mut self);
     fn fit(&mut self);
+
+    fn vs(&self, idx: usize) -> f64;
+    fn vs_mut(&mut self, idx: usize) -> &mut f64;
+
+    fn ms(&self, idx: usize) -> f64;
+    fn ms_mut(&mut self, idx: usize) -> &mut f64;
+
+    fn xs(&self, idx: usize) -> f64;
+    fn xs_mut(&mut self, idx: usize) -> &mut f64;
+
+    fn ns(&self, idx: usize) -> f64;
+    fn ns_mut(&mut self, idx: usize) -> &mut f64;
 }